Express search code intelligence as hook
Created by: lguychard
Stacked on #17513
As I was working on #17513 I realised we could greatly simplify how we hook up our search language code intelligence to the Monaco query input by using a ref for the search query, instead of an rxjs subject.
With this change, code intelligence logic for the monaco editor is now encapsulated in a useSourcegraphSearchCodeIntelligence
hook. Almost all RxJS usage has been removed.
And now I'll stop with my tech debt refactors, promise :)